In a network control system connecting, in the communication network, terminal units providing at least the chat function to make communication with the other terminal units on the real time basis while connecting the keyboard and exeucting mutual communication between the terminal units, the termnal unit which becomes the transmitting side describes the mode corresponding to the function to be executed and communication code under such mode within the communication command to be transmitted and indexes the connection timing table and also connects or disconnects the line for communication to the distant terminal unit on the basis of contents of the connection timing table in order obtain effective application of the communication network.
